The present invention relates to a sealing device for an universal joint and more particularly, to the sealing device for an universal joint for a propeller shaft used in a power transmission system of a motor vehicle.
A conventional sealing device for an universal joint is disclosed, for example, in JP 48-79954 or JP-U 61-23528. Such sealing device includes a resilient ring of rubber installed between a bearing cap arranged to a joint cross of the universal joint and a base of the universal joint, and having inner and outer lip portions which are in close contact with an end face of the bearing cap and a ridgeline portion between the end face of the bearing and a side surface thereof, respectively, thus sealing in lubricant around needle bearings, and releasing through the lip portions internal pressure produced in the bearing cap.
According to the above conventional sealing device for an universal joint, the inner and outer lip portions, namely, the dust lip portion positioned outside to be in close contact with the ridgeline portion between the end face of the bearing cap and the side surface thereof, and the oil lip portion positioned inside to be in close contact with the end face of the bearing cap, serve to seal the bearing cap. However, during electrodeposition painting taken place in the manufacturing process of the propeller shaft, a paint sticks on an outer peripheral surface of the dust lip portion as positioned outside, and solidifies with the drying, resulting in degradation of the resilient function. That is, part of the dust lip portion which is in close contact with the bearing cap loses resilient behavior, and falls in the hard contact state, accelerating wear and producing a reduction in the sealing function.
It is, therefore, an object of the present invention to provide a sealing device for an universal joint which contributes to prolongation of the longevity without any reduction in the sealing function.